Lightweight clumping animal litter and method thereof

ABSTRACT

Animal litter having up to a sixty percent reduction in bulk density can be produced by combining flat-shaped cellulosic materials and sodium bentonite clay. Not only is the resulting litter lighter, but it also maintains a high clump strength as compared to clay-based animal litters that contain greater than ninety percent by weight sodium bentonite clay.

THE FIELD OF THE INVENTION

Disclosed herein are lightweight clumpable animal litters. Specifically,disclosed herein are lightweight animal litters comprising compositeparticles of cellulosic materials and sodium bentonite that perform aswell as traditional clay-based, clumping litters, yet weigh up to sixtypercent less.

RELATED ART

Clay has long been used as a liquid absorbent and has found particularusefulness as an animal litter. Typically, the clay is mined, dried, andcrushed to the desired particle size. Some clay litters have the abilityto clump upon wetting. For example, sodium bentonite (aka Na-bentonite)is a water-swellable clay which, upon contact with moist animal waste,is able to agglomerate with other moistened sodium bentonite clayparticles. The moist animal waste is contained by the agglomeration ofthe moist clay particles into an isolatable clump, which can be removedfrom the container (e.g., litter box) housing the litter. The clumpstrength of clay litters containing equal or greater than ninety percentsodium bentonite are strong enough to hold the clump shape upon contactwith moisture and retain that shape upon scooping without pieces of thelitter breaking off of the clump and remaining in the litter box,allowing waste therein to create malodors. However, sodium bentoniteclay is very heavy and is mined. As such, it is a limited resource.

Another problem inherent in typical sodium bentonite clay litters is theinability to effectively control malodors. Clay has very poorodor-controlling qualities, and inevitably waste build-up leads tosevere malodor production. What is needed is a lightweight animal litterwith effective odor-controlling properties.

Accordingly, what is needed is an absorbent material suitable for use asan animal litter that uses less sodium bentonite, yet has clumpingcharacteristics equivalent to clay-based litters that contain at leastninety percent sodium bentonite litters. What is further needed is alightweight animal litter with odor-controlling properties that hasclumping properties comparable to clay-based litters containing greaterthan ninety percent sodium bentonite, yet that requires much lowerconcentrations of sodium bentonite.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a composite particle comprising wood chip and sodiumbentonite components.

FIG. 2 shows the particle to particle contact exhibited when roundparticles of the same size are used to form composite particles.

FIG. 3 shows the difference in volume between sixty percent by weightsodium bentonite and forty percent by weight wood chips.

FIG. 4 is a photograph of flat-shaped wood chips.

FIG. 5 is a graph showing the effect of varying amounts of kaolinite onthe brightness measured in % reflectance of a bentonite/cellulosic/PACcomposite particle animal litter.

FIG. 6 is a graph showing the effect of varying amounts of kaolinite onthe static charge present on bentonite/cellulosic/PAC composite particleanimal litter.

SUMMARY OF THE INVENTION

An aspect of the invention includes composite particles comprising aflat-shaped cellulosic material component having a mean particle size inthe range of about 3 mm to about 0.2 mm and an aspect ratio of at least2 and a powdered sodium bentonite component having a mean particle sizeless than about 0.25 mm. The composite particles may optionally containa spacer material having a particle size less than about 0.25 mm, suchas powder activated carbon (PAC), and may optionally contain a bindermaterial having a particle size less than about 0.25 mm, such as guargum. The composite particles can be used alone as an animal litter andexhibit a clump strength of at least 80 percent.

Another aspect of the invention includes composite particles comprisinga flat-shaped cellulosic material component having a mean particle sizein the range of about 3 mm to about 0.2 mm and an aspect ratio of atleast 2, a powdered sodium bentonite component having a mean particlesize less than about 0.25 mm, optionally a spacer material having a meanparticle size less than about 0.25 mm, such as powder activated carbon(PAC), optionally a binder material having a mean particle size lessthan about 0.25 mm, such as guar gum, dry blended with granular sodiumbentonite, calcium bentonite, kaolinite or mixtures thereof. Dryblending the composite particles with as little as 0.2% kaolinitesignificantly reduces the static charge build-up on the particles andsignificantly reduces the dark color attributable to the presence of PACcontained in the composite particles.

A third aspect of the invention includes a method of making thecomposite particles having a cellulosic material component and a sodiumbentonite component, the method comprising: providing flat-shapedcellulosic particles having a mean particle size in the range of about0.2 mm to about 3 mm; providing powdered sodium bentonite particleshaving a mean particle size less than about 0.25 mm, wherein the ratioof cellulosic material to sodium bentonite is in the range of about 1:4to about 4:1; using a high shear agglomeration process to mix thecellulosic particles and the sodium bentonite particles to formcomposite particles having a mean particle size in the range of about0.2 mm to about 3 mm.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before describing embodiments of the present invention in detail, it isto be understood that all publications, patents and patent applicationscited herein, whether supra or infra, are hereby incorporated byreference in their entirety to the same extent as if each individualpublication, patent or patent application was specifically andindividually indicated to be incorporated by reference in its entirety.

It must be noted that, as used in this specification and the appendedclaims, the singular forms “a,” “an” and “the” include plural referentsunless the content clearly dictates otherwise. Thus, for example,reference to an “additive” includes two or more such additives.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the invention pertains. Unless otherwise stated,amounts listed in percentage (“%'s”) are in weight percent.

Disclosed herein are composite absorbent particles that comprise asodium bentonite component and a cellulosic material component. Thecomposite absorbent particles have improved physical and chemicalproperties such that a lightweight litter can be produced withoutcompromising the performance of traditional clumping clay-based littersthat contain equal or greater than ninety percent sodium bentonite.Although sodium bentonite-based litters clump well, they also havedisadvantages. Sodium bentonite is very heavy, relatively expensive, andnot a renewable resource.

Disclosed herein are lightweight composite absorbent particlescomprising between about forty and about eighty percent by weight sodiumbentonite that maintain the clumping benefit of “pure sodium bentonite”(as defined herein). In preferred embodiments, a lightweight compositeparticle animal litter is disclosed that comprises as little as sixtypercent by weight sodium bentonite, yet retains the clump strength ofpure sodium bentonite litter. A high shear agglomeration process may beused to make the composite particles disclosed herein.

As used herein the term “pure sodium bentonite litter” means a clumpingclay-based litter that contains equal or greater than ninety percent byweight sodium bentonite. As used herein the term “composite particle”means a discrete particle that is formed by the combination of smallercomponent particles. As used herein the term “PAC” means powderedactivated carbon that is a fine black powder made from wood or othercarbon-containing materials (e.g., coconut, coal, etc.) that have beenexposed to very high temperatures in an airless environment and treated,or activated, to increase its ability to absorb by reheating withoxidizing gas or other chemicals. The result is a highly porous finepowder with a particle size less than about 0.25 mm and typicallyranging from about 50 to about 150 microns. As used herein the term“flat-shaped” means a particle having a length to height to depthrelationship wherein the following equation is greater than or equal to2: (length+width)/(2×depth). As used herein the term “cellulosicmaterial” means materials made from cellulose. Cellulose is complexcarbohydrate, (C₆H₁₀O₅)_(n), that is composed of glucose units. It formsthe main constituent of the cell wall in most plants. “Cellulosicparticles” are particles of cellulosic materials. Examples of cellulosicmaterials are discussed below. As used herein the term “clump strength”means the percentage of particles retained in the clump after threehours using the clump strength test described herein. As used herein theterm “high shear agglomeration process” means a high speed, conditioningand micro-pelletizing device that converts powder into smallagglomerates through the action of a high speed and the addition ofwater. As used herein the term “component” when used in conjunction witha composite particle means a small particle that was combined with othersmall particles to form a composite particle. As used herein the term“spacer material” means an agent that helps spread sodium bentonite onthe surface of a cellulosic component for better distribution of thesodium bentonite during the agglomeration process. As used herein theterm “binder” means a substance that causes the composite particles tobetter adhere to each other upon contact with a liquid, such as water orurine, to form a strong clump. Examples of binders include guar gum,starch, modified starch, natural hydrocolloids, alginates, acrylates andpolyvinyl acetate. Particle size ranges are determined by screeningmethods known in the art.

Cellulosic Materials

As used herein the terms “sawdust” and “shaving(s)” mean byproducts madeby fine wood particles as a result of cutting wood having a particlesize ranging from about 0.2 mm to about 3 mm, and preferably rangingfrom about 0.7 mm to about 2 mm. Sawdust refers to particles toward thesmaller end of the size range and shavings refer to particles toward thelarger end of the size range. FIG. 4 is a photograph of flat-shapedsawdust and shaving particles having a mean particle size in the rangeof about 3 mm to about 0.2 mm and an aspect ratio of at least 2.Collectively, these are referred to as “wood chips”. “Wood powder”refers to a composition of wood particles where the particles are allless than about 0.4 mm.

The surfaces of cellulosic particles, such as sawdust and shavings,whether they be derived from (wood, bark, leaves etc.), tend to behydrophobic due to the presence of hydrophobic substances such as resin,oil and wax, contained in plants and trees. These cellulosic particleswhen agglomerated without clay or other hydrophilic absorbent substancesmay have low absorbency and therefore not ideally suited for animallitter applications.

High shear agglomeration processes, such as pin mixing, can be used toform discrete composite particles. Pin mixing is a pin-type solidsprocessor designed for applications requiring high energy input tomaterials for mixing or micro-pelletizing. It is a high speed,conditioning and micro-pelletizing device that converts small particles(“components”) into discrete agglomerates (“composite particles”)through the action of high speed and the addition of water.

Use of a spacer material, such as activated carbon, aids in theagglomeration process by acting as an in situ pre-treatment for thecellulosic particles. Without being bound by theory, it is believed thatthe spacer material actually removes oil from the cellulosic particlesurfaces, either by absorption or other means, thereby facilitatingadequate wetting of the particle surfaces during agglomeration.Preferred spacer materials are inert, hydrophobic, and have a meanparticle size no larger than (and preferably smaller than) that of thesmallest component particle of the composite particle. Suitable spacermaterials include, for example, powder activated carbon, sodiumbicarbonate (baking soda), silica gel, activated alumina, and boroncompounds and may be effective at concentrations as low as about 0.3percent by weight of the composite particle.

Another feature common to some cellulosic materials, such as, woodchips, is that their particle structure remains well preserved duringhigh shear agglomeration processes due to its strength and elasticity.This property differs from mineral-based absorbent particles, such as,zeolites and clays; in that mineral-based particles tend to break anddisintegrate into smaller particles during high shear agglomerationprocesses before later binding to form composite particles. Having aparticle capable of maintaining its shape enables control of theresulting shape of the composite particles with less control of theagglomeration process parameters such as the speed or the moisturetarget. Flat-shaped cellulosic materials having a mean particle sizeranging from about 0.7 mm to about 2 mm are particularly preferred. Thepreferred weight percentage of flat-shaped cellulosic materials in thecomposite particles is between about 30 percent and about 50 percent.

Sodium Bentonite

Sodium bentonite powder having a mean particle size less than about 0.25mm is preferred. Sodium bentonite has an affinity to bind to itself, so,aside from the benefits already discussed, the use of a spacer materialcan act to reduce its stickiness thereby facilitating a more evendistribution of the sodium bentonite particles during the high shearagglomeration process.

Sodium bentonite expands when wet, absorbing as much as several timesits dry mass in water. The main mineral that forms bentonite isMontmorillonite ((Na,Ca)_(0.33)(Al,Mg)₂(Si₄O₁₀)(OH)₂.nH₂O).Na-montmorillonite, in particular, expands considerably more than otherclays (e.g., Ca-Montmorillonite) due to water penetrating the interlayermolecular spaces and concomitant adsorption. The presence of sodium asthe predominant exchangeable cation can result in the clay swelling toseveral times its original volume. Hence, its application in catlitters.

Adding a small amount of binder, such as guar gum, in an amount aslittle as 0.1 percent by weight can increase the clump strength of theresulting litter in some cases by up to ten percent. Preferred bindersinclude guar gum, starch, polyacrylates, polysaccharides, and alginates.Guar gum (“guar”) is particularly preferred because it is a powderedsolid that helps form strong and rigid clumps when wet and tends to bevery evenly distributed throughout the resulting composite particles.Thus, a very small amount of guar can have a considerable impact.Binders, such as guar, are known for their binding properties. They havebeen used in several cat litters to facilitate the adhesion betweenparticles thus, clumping. However, none of these composite particles(e.g., wood and guar, even in much higher concentrations) could achievethe high absorption and immediate clumping of Na-bentonite. On the otherhand, when mixing sodium bentonite with wood, the resulting compositeparticles are lightweight and strong and may or may not clump as well aspure Na-bentonite. Therefore, in some cases a binding agent may aid withclumping.

In order to achieve maximum performance the binder needs to bind to anadequate surface (e.g., a rough and solid surface). Clay, such sodiumbentonite is made from several micrometric crystals that tend todisintegrate under pressure or moisture. Therefore, intermediate fillerhelps achieve higher binding strength. Adding cellulosic materials(e.g., wood chips), provide structural integrity to the compositeparticles in a manner analogous to the way re-bar strengthen concrete. Abinder, such as guar, can help bind wood particles to each other and toclay. This synergy between clay, wood and binder has resulted in highclumping composite particles similar to Na-bentonite bentonite. Othersuitable binders may include starches, alginates, and polysaccharides.Minimizing the amount of binder necessary is desirable because of cost.

Composite Particles

The composite particles disclosed herein comprise a flat-shapedcellulosic component having a mean particle size ranging from about 0.2to about 3 mm (preferably about 0.7 mm to about 2 mm) in an amountranging from about 20 percent to about 80 percent (preferably from about40 percent to about 60 percent) by weight and a sodium bentonitecomponent having a mean particle size less than about 0.25 mm in anamount ranging from about 20 percent to about 80 percent (preferablefrom about 40 percent to about 60 percent) by weight. The resultingcomposite particles have an interlocking structure as shown in FIG. 1which allow for more particle to particle surface contact 6 as comparedto the particle to particle contact 6 exhibited in the round particlesshown in FIG. 2. Referring to FIG. 1, the combination of a flat-shapedcellulosic component 4 having a mean particle size ranging from about0.2 mm to about 3 mm (preferably about 0.7 mm to about 2 mm) in anamount ranging from about 20 percent to about 80 percent (preferablyabout 40 percent to about 60 percent) by weight and a sodium bentonitecomponent 2 having a mean particle size less than about 0.25 mm in anamount ranging from about 20 percent to about 80 percent (preferablyabout 40 percent to about 60 percent) by weight allows for an efficientuse of the sodium bentonite so that the amount of sodium bentonite canbe significantly reduced without substantially sacrificing the clumpstrength of the litter (see Table 5) because the contact betweencomponent particles of the composite particle is maximized. The malodorpath 8 is also more restricted as compared to the malodor path 8 shownin FIG. 2.

Additionally, an amount ranging from about 0.1 to about 2 percent(preferably about 0.3 percent to about 1 percent) PAC can be included inthe composite particles depicted in FIG. 1. As used herein the term“bentonite/cellulosic/PAC composites” is defined as a composite particlecomprising a flat-shaped cellulosic component having a mean particlesize ranging from about 0.2 mm to about 3 mm (preferably 0.7 mm to about2 mm) in an amount ranging from about 35 to about 45 percent by weight,a sodium bentonite component having a mean particle size less than about0.25 mm in an amount ranging from about 55 to about 65 percent byweight, a PAC component in an amount ranging from about 0.3 to about 1percent by weight, and a guar gum component in an amount ranging from 0percent to about 1 percent by weight.

For example, referring to FIG. 2, if a high shear agglomeration processwere used to agglomerate a mineral-based material such as a zeolite 10having a mean particle size ranging from about 0.2 mm to about 3 mm inan amount ranging from about 20 percent to about 80 percent by weightand a sodium bentonite component 2 having a mean particle size less thanabout 0.25 mm in an amount ranging from about 50 to about 80 percent byweight, the resulting composite particle would likely look like thecomposite depicted in FIG. 2 and the clump strength of the resultingcomposite particle would be expected to be significantly reducedcompared to the clump strength of pure sodium bentonite (see Table 3).This is because, as discussed, mineral-based absorbent materials such aszeolites and clays tend to disintegrate into smaller particles duringhigh shear agglomeration processes before later binding to formcomposite particles.

Still referring to FIG. 2, the same would be true if a high shearagglomeration process were used to agglomerate a cellulosic materialsuch as a wood powder 10 having a mean particle size less than about0.25 mm in an amount ranging from about 20 percent to about 80 percentby weight and a sodium bentonite component 2 having a mean particle sizeless than about 0.25 mm in an amount ranging from about 50 percent toabout 80 percent by weight. The resulting composite particle wouldlikely look like the composite depicted in FIG. 2 and the clump strengthof the resulting composite particle would be expected to besignificantly reduced compared to the clump strength of pure sodiumbentonite (see Table 3). This is because fine cellulosic materials evenwhen keeping the structural integrity of their shape, are the same sizeas the bentonite particles and the contact between component particles 6of the composite particle is minimized. Additionally the malodor path 8is less restricted which is expected to result in less overall odorcontrol.

The inventors have surprisingly found that particle size of cellulosicparticle contributes to the clump strength of the resultingbentonite/cellulosic/PAC composites to an even greater extent thananticipated. The inventors made two samples of bentonite/cellulosic/PACcomposites by pin mixing about 50% cellulosic particles, about 48.5%sodium bentonite powder, about 0.5% guar gum and about 1% PAC. The firstsample was formed from powdered cellulosic particles having a meanparticle size less than about 0.4 mm, powdered sodium bentoniteparticles having a mean particle size less than about 0.25 mm andpowdered guar gum and PAC having a mean particle size less than about0.25 mm. The second sample was formed from wood chips having a meanparticle size ranging from about 0.7 mm and about 2 mm, powdered sodiumbentonite particles having a mean particle size less than about 0.25 mmand powdered guar gum and PAC having a mean particle size less thanabout 0.25 mm. The first sample did not clump, whereas the second sampleexhibited a clump strength of about 92. Thus, the inventors concludedthat the particle size of the cellulosic particles contributessignificantly to the resulting clump strength of thebentonite/cellulosic/PAC composites.

Having flat-shaped cellulosic particles that retain their shape duringhigh shear agglomeration processes and are larger than the sodiumbentonite particles allows the sodium bentonite to flow evenly among thecellulosic particles which creates a resulting composite particle thathas a requisite amount of porosity to allow liquid to enter the particleand disperse throughout the composite particles enabling the sodiumbentonite components to interact and bind together. As discussed, theaddition of spacer materials no larger in size than the sodium bentoniteparticles to the agglomeration process is believed to minimize thesodium bentonite's affinity to bind to itself during the agglomerationprocess and therefore increase the porosity of the resulting compositeparticle.

Additionally, without being bound by theory, it is believed that thecellulosic components take a longer time to absorb liquids than clays.It is therefore believed that the sodium bentonite absorbs liquid andholds it in close proximity to the cellulosic component such that theliquid slowly transfers or wicks to the cellulosic component. Wood is aheterogeneous, hygroscopic, cellular and anisotropic material. It iscomposed of cells, and the cell walls are composed of micro-fibrils ofcellulose (40%-50%) and hemicellulose (15%-25%) impregnated with lignin(15%-30%). The water diffusivity of wood (the rate at which water movesfrom the surface to the interior of wood particles) can be reducedsignificantly depending on the porous structure of wood and thereactivity of its chemical components. Adding clay, such as sodiumbentonite, (high water diffusivity), in contact with the surface of woodparticles, increases the overall diffusivity of the resulting compositeparticles (clay/wood). Therefore, it is believed that sodium bentoniteabsorbs liquid and holds it in close proximity to the cellulosiccomponent such that the liquid slowly transfers or wicks to thecellulosic component. The result is highly absorbent composite particlesthat immediately clump upon hydration similar to pure sodium bentoniteclay particles.

Bulk Density Reduction can be as high as about 60% as compared to puresodium bentonite litter. Bulk density is a property of powders, granulesand other “divided” solids, especially used in reference to mineralcomponents. It is defined as the mass of the many particles of thematerial divided by the total volume they occupy. The total volumeincludes particle volume, inter-particle void volume and internal porevolume. Bulk density is not an intrinsic property of a material; it canchange depending on how the material is handled. For example, a powderpoured into a cylinder will have a particular bulk density; if thecylinder is disturbed, the powder particles will move and usually settlecloser together, resulting in a higher bulk density. Bulk density is ameasure of the weight of the litter per unit volume (g/cc). The testmethod used to measure bulk density comprises a hopper with a pintcontainer underneath. The hopper is filled with approximately 2000 cc ofthe sample. The gate situated at the bottom of the hopper is opened tofill the pint container with material until it overflows. The containeris then leveled out using a straight edge tool and the weight isrecorded. The same process is repeated twice and an average of threereps is reported (g/cc or lb/cf).

Referring to FIG. 3, a composition comprising about sixty percent byweight sodium bentonite 2 and about forty percent by weight wood chips 4is about equal to a composition comprising only about twenty percent byvolume sodium bentonite 2 and about eighty percent by volume wood chips4. The inventors have found that pin mixing such 20:80 by volume ratioof Na-bentonite and flat-shaped wood particles with about 1% guar gum,yields a litter with a clump strength equivalent to that of pure sodiumbentonite (see Table 3).

Clump strength is measured by first generating a clump by pouring 10 mlof pooled cat urine (from several cats so it is not cat specific) onto a2 inch thick layer of litter. The urine causes the litter to clump. Theclump is then placed on a half inch screen after a predetermined amountof time 3 hours has passed since the particles were wetted. The screenis agitated for 5 seconds with the arm up using a Ro-Tap MechanicalSieve Shaker made by W. S. Tyler, Inc or other similar device. Thepercentage of particles retained in the clump is calculated by dividingthe weight of the clump after agitation by the weight of the clumpbefore agitation. The clump strength indicates the percentage ofparticles retained in the clump after 3 hours. Ideally, greater than90%, and more ideally, greater than 95% of the particles will beretained in a clump after 3 hours upon addition of an aqueous solution,such as deionized water or animal urine. Greater than 80% particleretention in the clump is preferred.

Attrition values measure the percentage of breakage, size reduction, orfragmentation of the composite particles. ASTM method E-728 StandardTest Method for Resistance to Attrition of Granular Carriers andGranular Pesticides was used to measure attrition.

Kaolinite

One disadvantage of the bentonite/cellulosic/PAC composites disclosedherein is that they tend to be somewhat dark in color due to the carbonthat is contained in the particles. The inventors have found that thecolor of the animal litter can be made brighter by dry blending verysmall amounts of kalolinte (as low as about 0.2% by weight) with thebentonite/cellulosic/PAC composites disclosed herein.

Another disadvantage of the bentonite/cellulosic/PAC compositesdisclosed herein is that reducing the bulk density of the litter tendsto increase the tracking. The inventors observed that the compositeparticles tend to carry an elevated static charge as compared to puresodium bentonite litter. This static charge leads to an undesirableamount of tracking because the static electricity causes the compositelitter particles to cling to the animals' fur. The inventors havesurprisingly found that the amount of static can be significantlyreduced by dry blending very small amounts (as low as about 0.2% byweight) of kaolinite with the bentonite/cellulosic/PAC composites.Initially added as a whitening agent to counteract the dark color of thecarbon and enhance the litter's appearance, the inventors have foundthat kaolinite provides an unexpected anti-static effect.

Kaolinite is a common phyllosilicate mineral. Since it is relativelyinert and long lasting, kaolinite has several industrial uses. It isused as a filler for paint, rubber and plastics. However, the greatestindustrial demand for kaolinite is in the paper industry to produce aglossy paper. Kaolinite's structure is composed of silicate sheets(Si2O5) bonded to aluminum oxide/hydroxide layers (Al2(OH)4) calledgibbsite layers. Kaolinite forms from the alteration (mostly weathering)of aluminum rich silicate minerals such as feldspars. Kaolinite is awhite clay capable of mixing with carbon and improving its appearance incat litter.

The inventors have shown that dry blending at least about 0.2% kaoliniteby weight to the bentonite/cellulosic/PAC composites disclosed herein,can significantly brighten the dark color of thebentonite/cellulosic/PAC composites when used as an animal litter. Thebrightness (in percent reflectance) of the animal litter was evaluatedusing a Minolta Chroma Meter CR-300. This device is a compacttristimulus color analyzer for measuring colors of surfaces includingtextured surfaces: the higher the number, the brighter the surface ofthe material measured. Table 1 and FIG. 5 show the effect of varyingamounts of kaolinite on the brightness of a bentonite/cellulosic/PACcomposite particle animal litter.

TABLE 1 Percent Colorimetric Results (percent reflectance) KaoliniteSample 1 Sample 2 Sample 3 Sample 4 Sample 5 Average st. dev.   0% 50.051.0 51.3 51.8 50.0 50.8 0.81 0.1% 51.4 51.2 50.3 51.6 51.5 51.2 0.540.2% 52.0 52.2 51.7 52.3 52.3 52.1 0.26 0.5% 54.2 53.9 53.9 54.3 54.254.1 0.17   1% 55.1 55.4 55.3 54.8 55.2 55.2 0.21   2% 56.2 56.6 57.657.4 57.3 57.0 0.56

The inventors have shown that adding at least about 0.2% kaolinite byweight to the bentonite/cellulosic/PAC composites disclosed herein, cansignificantly reduce the static charge present on the compositeparticles when used as an animal litter. As shown in Table 2 below andFIG. 6, kaolinite dry blended with the bentonite/cellulosic/PACcomposites at levels as low as about 0.2% by weight significantlyreduces the static charge observed. This, in turn, correlates to asignificant reduction in tracking when the bentonite/cellulosic/PACcomposites disclosed herein are used as an animal litter.

Static charge in animal litter was evaluated using the following testmethod. Bentonite/cellulosic/PAC composites (about 59% Na-bentonite,about 38% wood chips, about 1% PAC and about 0.5 guar gum) comprised theanimal litter. This animal litter was used as a control (0% kaolinite).The control then was mixed with powder kaolinite at the levels mentionedin Table 2. One hundred cubic centimeters (100 cc) of each product wasthen poured in a one hundred cubic centimeter (100 cc) plasticcontainer, mixed and poured out of the container by gravity. Theremaining particles bound to the plastic container walls were removedmanually from the container and weighed. As illustrated in Table 2 andFIG. 6, the static charge in the animal litter was completelyneutralized at about 0.2% of powder kaolinite.

TABLE 2 Percent Amount of particles bound to the plastic jar afterpouring the contents out. Kaolinite Sample 1 Sample 2 Sample 3 Sample 4Sample 5 Average st. dev.   0% 124 133 117 127 136 127 7 0.1% 14 18 2625 28 22 6 0.2% 0 0 0 0 0 0 0 0.5% 0 0 0 0 0 0 0   1% 0 0 0 0 0 0 0   2%0 0 0 0 0 0 0Composite Particle Litter Compositions

Litter Composition A was prepared by pin-mixing 69% Na-bentonite, 30%wood chips, and 1% PAC. Litter Composition B was prepared by pin-mixing59.5% Na-bentonite, 40% wood chips, and 0.5% PAC. Litter Composition Cwas prepared by pin-mixing 59.5% Na-bentonite, 39% wood chips, 1% PACand 0.5% guar gum. Litter Composition D is a commercially available puresodium bentonite litter (as defined herein). Litter Composition E wasprepared by pin-mixing substantially spherical cellulostic particleshaving a particle size range less than 1 mm and sodium bentonite havinga size range of less than 1 mm. Litter composition F was prepared by dryblending forty percent 8/30 mesh wood sawdust with sixty percent 8/40mesh Na-bentonite.

The clump strength, attrition and bulk density were measured for allcompositions. Bulk density reduction value is shown as compared to puresodium bentonite litter (as defined herein). The results shown in Table3 below are the average values from several repetitions.

TABLE 3 Bulk Density Clump Bulk Density Reduction Composition StrengthAttrition (g/cc) (%) A 90 1.52 0.62 42 B 80 0.4 0.53 51 C 95 1.3 0.48 56D 92 N/A 1.08 N/A E 0 (litter 0.54 0.91 20 did not clump) F 25 N/A 0.3865Animal Litter Compositions

Although the bentonite/cellulosic/PAC composites disclosed herein,either alone or dry blended with kaolinite, are suitable for use as ananimal litter, the inventors have found that using thebentonite/cellulosic/PAC composites disclosed herein as a component toan animal litter, either alone or dry blended with kaolinite asdescribed above, yields excellent results. Combining thebentonite/cellulosic/PAC composites disclosed herein with granular clayparticles results in an animal litter that exhibits excellent clumpstrength, odor control, bulk density reduction (BDR), tracking, colorand static control. Combining the composite particles with granular claysimplifies the manufacturing process of the animal litter. The compositeparticles may comprise about 2 to about 65 percent by weight of theanimal litter, the granular sodium bentonite may comprise about 35 toabout 98 percent by weight of the animal litter, and the granularcalcium bentonite may comprise 0 to about 15 percent by weight of theanimal litter.

Samples were made at three different BDR levels: about 15%, about 30%and about 40%. The samples comprised the bentonite/cellulosic/PACcomposites disclosed herein, granular calcium bentonite, granular sodiumbentonite and optionally small amounts of litter additives such askaolinite, borax, fragrance, etc. As used herein “granular Ca-bentonite”and “granular Na-bentonite” refer to calcium bentonite clay particlesand sodium bentonite clay particles approximately 8/40 mesh (about 0.4mm to about 2 mm).

Bentonite/cellulosic/PAC composites were prepared by pin-mixing about60% Na-bentonite, about 40% wood chips, and about 1% PAC. No binder wasincluded. Litter Composition G was prepared by dry blending about 5% ofthe bentonite/cellulosic/PAC composites by weight with about 0.1%kaolinite, about 10% by weight granular Ca-bentonite clay, and about 84%by weight granular Na-bentonite clay. Litter Composition H was preparedby dry blending about 20% the bentonite/cellulosic/PAC composites withabout 0.3% kaolinite, 10% granular Ca-bentonite clay, and about 58%granular Na-bentonite clay. Litter Composition I was prepared by dryblending about 60% by weight the bentonite/cellulosic/PAC compositeswith about 0.3% by weight kaolinite, 10% granular Ca-bentonite clay, andabout 28% by weight granular Na-bentonite clay. Table 4 compares theperformance of the litter compositions G-I with the pure sodiumbentonite commercial litter composition D.

TABLE 4 Bulk Density Clump Dust Bulk Density Reduction CompositionStrength (mg) (g/cc) (%) G 91 38 0.90 16.5 H 92 40 0.77 29 I 95 33 0.6638.8 D 92 37 1.08 N/A

Table 5 shows the particle size distribution for the various samples G-Iagainst the commercially available pure sodium bentonite litterComposition D.

TABLE 5 Mesh size Composition 4 8 12 16 20 30 40 60 100 Pan G 0.1 0.3 1218 21 26 18 2.6 0.7 1.2 H 0.1 0.3 14 24 29 23 10 0.7 0.08 0.2 I 0.05 0.611 25 33 23 7 0.5 0.1 0.2 D 0.04 0.6 17 24 20 20 12 6 1 0.5

Two additional lightweight formulas were made and compared to twocommercially available pure sodium bentonite litters.Bentonite/cellulosic/PAC composites were prepared by pin-mixing about58% Na-bentonite, about 38% wood chips, and about 1% PAC and about 0.5%guar gum. Litter Composition J was prepared by dry blending thebentonite/cellulosic/PAC composites above with about 0.5% kaolinite andoptionally minor amounts of other litter additives such as fragrance.Composition J was compared to commercially available pure sodiumbentonite litter (as defined herein) Composition D.

Bentonite/cellulosic/PAC composites were prepared by pin-mixing about58% Na-bentonite, about 38% wood chips, and about 0.5% PAC and about0.5% guar gum. Litter Composition K was prepared by dry blending thebentonite/cellulosic/PAC composites above with about 0.5% kaolinite andoptionally minor amounts of other litter additives such as fragrance.Composition K was compared to a second commercially available puresodium bentonite litter (as defined herein) Composition L. Particle sizedistribution (PSD) is the range in which at least 80% of the particlesfall within. Odor control is measured by the Malodor Sensory Methoddescribed below. Samples were measured on Day 7 and Day 10. Bothcommercially available litter compositions D and L contained fragrance.In addition to the malodor ratings, litter Compositions J and K wereobserved to have significantly higher fragrance scents on both day 7 andday 10 than the pure sodium bentonite commercially available litters.

Description of Malodor Sensory Method:

-   -   1. Cat boxes are filled with test litter to 3-4 inches    -   2. Boxes are dosed each day with urine and feces.    -   3. On day 7 the boxes are placed into sensory booths for        evaluation.    -   4. The boxes are allowed to equilibrate in the closed booths for        ˜15 minutes before panelist evaluation.    -   5. The samples are then rated on a 15 point line scale by        trained panelists.    -   6. The boxes are then scooped and re-dosed again to complete 10        days cycle of dosing.    -   7. On day 10 the boxes are placed into sensory booths for        evaluation.    -   8. The boxes are allowed to equilibrate in the closed booths for        ˜15 minutes before panelist evaluation.    -   9. The samples are then rated again on a 15 point line scale by        trained panelists.

TABLE 6 Bulk Clump Odor Control PSD Attrition Density Bulk DensityComposition Strength Dust (mg) (Day 7/Day 10) (mesh) (wt. percent)(g/cc) Reduction (%) J 95 35 6/28 14/30 0.9 0.5 52 D 91 72 5/32 10/202.5 1.07 N/A K 94 26 5/29 14/30 0.7 0.5 53 L 94 68 6/25 10/30 2.06 1.08N/A

Thus, the described embodiments are to be considered in all respectsonly as illustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes that come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

We claim:
 1. Composite particles suitable for use as an animal litter comprising: a flat-shaped cellulosic material component having a mean particle size ranging from 0.2-3 mm and having an aspect ratio of at least 2; a powdered sodium bentonite component having a mean particle size less than 0.25 mm; wherein the ratio of cellulosic material to sodium bentonite ranges from 1:4 to 4:1 and wherein the mean particle size of the composite particles ranges from 0.4-4 mm; and wherein the composite particles when used as an animal litter have a clump strength of at least 80%.
 2. The composite particles recited in claim 1 further comprising a spacer material having a mean particle size less than 0.25 mm.
 3. The composite particles recited in claim 1 further comprising a binder having a mean particle size less than 0.25 mm.
 4. The composite particles recited in claim 1 further comprising a spacer material having a mean particle size less than 0.25 mm and a binder having a mean particle size less than 0.25 mm.
 5. An animal litter comprising a dry blend of: (i) composite particles comprising (a) a flat-shaped cellulosic material component having a mean particle size in the range of 0.2-3 mm; where the aspect ratio is at least 2 (b) a powdered sodium bentonite component having a mean particle size less than 0.25 mm, wherein the ratio of cellulosic material to sodium bentonite is in the range of 1:4 to 4:1 and wherein the mean particle size of the composite particles is in the range of 4-0.4 mm; (c) optionally a spacer material, and (d) optionally a binder; (ii) granular sodium bentonite having a mean particle size in the range of 0.4-2 mm; and (iii) optionally granular calcium bentonite having a mean particle size in the range of 0.4-2 mm; wherein the animal litter has a clump strength of at least 80%.
 6. The composite particles recited in claim 5, wherein the spacer material is selected from the group consisting of PAC, silica gel, zeolite, calcium bentonite, limestone, gypsum, kaolinite, silica, hydrophobic silica, flow aid such as talk, starches and combinations thereof.
 7. The composite particles recited in claim 5, wherein the binder is selected from the group consisting of guar gum, modified starch, natural hydro-coloids, alginates, acrylates, poly vinyl acetate, and combinations thereof.
 8. A method of making composite particles having a cellulosic material component and a sodium bentonite component comprising: providing flat-shaped cellulosic particles having a mean particle size ranging from 0.2-3 mm; providing powdered sodium bentonite particles having a mean particle size less than 0.25 mm, wherein the ratio of cellulosic material to sodium bentonite is in the range of 1:4 to 4:1; using a high shear agglomeration process to mix the cellulosic particles and the sodium bentonite particles to form composite particles having a mean particle size in the range of 0.4-2 mm. 